Chemical characterization and phase behaviour of grape seed oil in compressed carbon dioxide and ethanol as co-solvent Irede Dalmolin a , Marcio A. Mazutti b , Eduardo A.C. Batista a , M. Angela A. Meireles a , J. Vladimir Oliveira b, * a Department of Food Engineering, School of Food Engineering, Rua Monteiro Lobato, 80, University of Campinas – UNICAMP, 13083-862 Campinas, SP, Brazil b Department of Food Engineering, URI À Campus de Erechim, Av. Sete de Setembro, 1621, 99700-000 Erechim, RS, Brazil article info Article history: Received 15 December 2009 Received in revised form 2 February 2010 Accepted 3 February 2010 Available online 8 February 2010 Keywords: Phase equilibrium data Grape seed oil Carbon dioxide Ethanol abstract The aim of this work is to report phase equilibrium experimental results for the systems grape oil/carbon dioxide and (grape oil/carbon dioxide + ethanol). The oil was obtained by supercritical extraction from the grape seed residue from wine production. The static synthetic method using a variable-volume view cell was employed for obtaining the experimental bubble and dew (cloud) points transition data over the temperature range of (313.15 to 343.15) K and pressures up to 20.6 MPa. The experiments were carried out using (ethanol + CO 2 ) overall mass fractions ranging from 0.50 to 0.99, keeping a fixed ethanol to car- bon dioxide molar ratio at 1:3. Results indicate the existence of complex phase behaviour for all temper- atures investigated with the occurrence of vapour–liquid, liquid–liquid and vapour–liquid–liquid phase transitions observed. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The wine industry is a relatively recent economic activity in Brazil when compared to traditional producing countries from Eur- ope. The expected growth of wine-making [1] will increase the vol- ume of waste and the consequent accumulation of this by-product is likely to become a serious environmental problem. Grape seed is a by-product of the wine fermentation and is generally used for animal feed or disposed of by burning. An alternative destination to this residue may be the extraction of seed oil, recognized as a valuable commodity for the production of high-value added products. Grape seed oil is rich in unsaturated fatty acids, such as linoleic and oleic acid and contains mono and diglycerides. It can offer many advantages for human consumption as it also contains monomeric flavan-3-ols, phenolic acids and oligomeric proantho- cyanidins, which exhibit potential antioxidant activity [2]. Accord- ingly, food, pharmaceutical and cosmetic industries have shown a great interest for the grape seed oil due to its properties. Industrially, vegetable oil seeds are obtained by extraction from a solid matrix by mechanical pressing and organic solvent extrac- tion. During pressing, most of the oil is extracted from the seeds, but usually a considerable amount still remains in the final cake with a solvent being necessary as a second extraction step. Tradi- tionally, n-hexane has been employed, but in spite of the process being very efficient, possible thermal degradation of the oil and incomplete solvent elimination from (500 to 1000) Á 10 À6 residue are the main drawbacks of this process [3]. Supercritical carbon dioxide (SC-CO 2 ) is a suitable solvent to produce such oils, offering a number of advantages. It is easily separated, leaving virtually no traces in the process matrix. It is safe, and readily available at low cost. In addition, it allows operations at relatively low pressures and at near-room temperatures, thus helping to minimize the product thermal degradation [4]. Indeed, supercritical-fluid extrac- tion (SFE) applied to the processing of natural products such as natural pigments, and aromas, has received a lot of attention in the past two decades. In the South America, it has found several applications mainly due to the rich biodiversity of this region [5]. The use of co-solvents in SFE (small amounts of organic solvents combined with supercritical carbon dioxide) has been employed to enhance the efficiency of the extraction by increasing yield and modifying the selectivity of the process. The co-solvent may change the solvent mixture (CO 2 and co-solvent) characteristics such as polarity and specific interactions with the solute forming hydrogen bonds or interacting with active sites of solid matrix [6]. Some authors [7,8] studied the use of ethanol as co-solvent to obtain supercritical extracts and observed that the solubility of the oil increased with the increase of co-solvent concentration. Regarding the extraction of grape seed oil using compressed flu- ids, some works can be found in the literature with carbon dioxide focusing on the fractionation of compounds present in the oil [9], the study of the process parameters and characteristics of the raw material to be extracted [10–12], solubility of grape seed oil 0021-9614/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2010.02.003 * Corresponding author. Tel.: +55 54 35209000; fax: +55 54 35209090. E-mail address: vladimir@uricer.edu.br (J.V. Oliveira). J. Chem. Thermodynamics 42 (2010) 797–801 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct